Process of producing sand molds for molding stone pattern plates



' the known processes of Patented July 5, 192?.

UNITED STATES PATENT/OFFICE.

xm'wnnnna, or nusnnm GERMANY.

PROCESS OF PBODUQING AND HOLDS FOB; HOLDING STONE PATTERN PLATES.

'10 Drawing. Application filed January The object of this invention is a process of producing sand molds for molding stone pattern plates. This process differs from producing sand molds for molding pattern plates in foundries and other plants in so far as by means of sand molds made after this process stone pattern plates can be'produced which do not shrink and which, at the sametime, are equal inv strength to pattern plates made of metal in the usual manner.

By meansof this process molds are produced which are perfectly smooth on their outer surface and which do not show the more or less granular structure of the sand as do the sand molds hitherto in use; The molds, to which the present invention relates, are temporary molds which are. used only once.

The use of sand molds for casting gypsum, cement, marble cement, caseine masses etc. for the purpose of producing figures, reliefs and pattern plates for foundries etc. is well known but the objects after the known processes showed the same roughness of surface as the sand molds owing to the tendency of sand molds of the known type to deprive the above-mentioned masses of theirdissolvent, for example water or magnesium chloride. This tendency resulted in the shrinking or sinking in of the above-mentioned masses, and, at the same time, in a considerable reduction of, their hardness, which, on the other hand, did not take place, if the masses were poured into non-porous molds impermeable to liquids,

and it is the fundamental idea. on which this new process is based to eliminate the roughness of the surface of the sand molds, to make them smooth and impermeable to liquids so that the material poured .into these molds is no longer deprived of its dis'solvent and remains much harder. V

7 To produce the effect described above the sand isimpregnated before being molded. I am aware of the fact that a process is known of impregnating sand before molding by treating it with solid chlorate or a saturated solution of chlorate. .The' addition of chlorate causes a chemical action and reaction between the salt and the material poured into the mold for the purpose of im:

parting a hard surface to the models. The resent invention, however, does not aim at imparting a hard surface to the models and 1a, 1925. Serial ll'o. a,s41.'

the material used in making them but to ing material like sand, 'while the objects thus produced need only very little finish-' ng. Qf special importance is the present invention in regard. to the production of pattern material in foundries, as the'pattern plates made after thisprocessdo not shrink and can be .quicker and more cheapli made than metal plates. By means of t e sand molds, on which the process is based, pattern plates are produced perfectly equal in value to metal plates. The process' consists in mixing the. sand prior to molding with resins, or 'vegetable pitches, and by heating the surface of the mold later on. By the process outlined-here there is formed on the surface of the sand mold a fine film of glass-like coating, resin, varnish etc. which smoothes the roughness of the sand by covering its pores and rendering it impermeable to the dissolvents of the material to be poured into it.

The aim of the present invention is attainedalso by first molding the sand and impregnating its surface shortly before use by powdering the sand mold with pulverized resins, or vegetable pitches and by s'ubjectingit to the action of a flame later on, or by'merel powdering the sand mold with sootortac. i

s Models formed in' these molds will also show a smooth surface, and will exactly cogupspond to the dimensions of their originils, as the methods outlined above will smooth-the roughness of the sand and make it impermeable to the dissolvents of the main molding the sand first, impregnating its s gnature.

surface shortly before use by powdering it with pulverized vegetable pitches and slightly heating it, whereupon'the liquid 10 modelling mass is poured in. a In testimony whereof I have afiixed my KARL WERNER. 

